#include<stdio.h>
/*int main()
{
	long num=0;
	long sum = 0L;
	_Bool int_put;
	printf("Please enter an integer to be summed ");
	printf("(q to quit):");
	int_put = 1;
	/*int_put = (scanf_s("%ld", &num) == 1);*/
	/*while (int_put)
	{
		sum += num;
		printf("Please enter next integer (q to quit):");
		int_put = (scanf_s("%ld", &num) == 1);
	}
	printf("Those integers sum to %ld.\n", sum);
	return 0;
}*/
#include<stdio.h>
int f(int n)
{
	if (n == 1 || n == 2)return 1;
	else return f(n - 1) + f(n - 2);
}
void main()
{
	int n = 0;
	scanf_s("%d", &n);
	printf("%d", f(n));
}